Discussion :
This is a cosmetic issue with the PCI passthrough. Functionally, it works fine for the supported devices. The reason is pci.ids available in PCI source forge site was not carrying Next IO and PLX Bridge's device IDs. Though the source forge is updated with the IDs now, ESXi 5.1 does not carry these hence the devices are marked as unknown.

Resolution :
VMware is aware of the issue and the updated pci.ids is going to be part of the ESXi 5.1 update 2 release.

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